In the art of container manufacture, the term "container finish" generally refers to that portion of the container which defines the container mouth. In a bottle, for example, the finish includes that portion of the container neck having threads and/or shoulders for receiving the container cap, as well as the upper surface of the neck surrounding the container mouth against which the cap seats. It is important that the container finish be properly manufactured so that a cap may be affixed thereto to seal the container cavity against leakage and escape of carbonation during handling and storage.
Conventional technology for mass production of glass or plastic containers involves forming the containers in a multiplicity of blow-molds Various types of faults or checks, termed "commercial variations" in the art, may occur. It has heretofore been proposed to employ optical scanning techniques for inspecting such containers for variations which affect optical transmission characteristics of the container sidewall In U.S. Pat. Nos. 4,378,493, 4,378,494 and 4,378,495, all of which are assigned to the assignee of the present application, there are disclosed methods and apparatus in which glass containers are conVeyed through a plurality of stations where they are physically and optically inspected. At one inspection station, a glass container is held in vertical orientation and rotated about its vertical axis. An illumination source directs diffused light energy through the container sidewall. A camera, which includes a plurality of light sensitive elements or pixels oriented in a linear array parallel to the vertical axis of container rotation, is positioned to view light transmitted through a vertical strip of the container sidewall. The output of each pixel is sampled at increments of container rotation, and event signals are generated when adjacent pixel signals differ by more than a preselected threshold level. An appropriate reject signal is produced and the rejected container is sorted from the conveyor line.
U.S. Pat. No. 4,701,612, assigned to the assignee hereof, discloses a method and apparatus for inspecting the finish of transparent containers, particularly glass containers, which include facility for directing diffused light energy laterally through the container finish as the container is rotated about its central axis. A camera includes a plurality of light sensitive elements or pixels disposed in a linear array angulated with respect to the container axis and coplanar therewith to view the external and internal finish wall surfaces, the latter through the open container mouth. Individual elements of the camera linear array are sampled by an information processor at increments of container rotation, and corresponding data indicative of light intensity at each element is stored in an array memory as a combined function of element number and scan increment. Such data is compared following completion of container rotation to standard data indicative of an acceptable container finish, and a reject signal is generated if such comparison exceeds an operator-adjustable threshold. Although the method and apparatus so disclosed represent a significant advance in previous finish inspection techniques and have enjoyed acceptance in the art, improvement remains desirable. For example, the method and apparatus so disclosed, while highly effective in detecting horizontal variations in the container finish, are not as effective in detecting vertical and radial variations. Furthermore, the disclosed apparatus cannot measure geometric characteristics of the container finish such as inside diameter, outside diameter or thread diameter.
U.S. Pat. No. 4,492,476 discloses an optical inspection system for transparent containers in which an image of a test container is directed onto an array camera which includes a two-dimensional CCD image sensor. Sensor elements or pixels are scanned by column parallel to the container axis, and circuitry is responsive to detection of the image edges for identifying an inspection region containing the container image, and for processing image data for variation detection only within such inspection region. However, all image data must be scanned for identifying the inspection region. Furthermore, image data processing is accomplished entirely at the processing circuitry. As a result, the disclosed technique is more time consuming than desirable for inspecting containers in a mass production environment. Moreover, the disclosed system does not measure geometric characteristics of containers.
U.S. Pat. No. 4,430,673 discloses an optical star tracker for spacecraft attitude control which employs a CCD image sensor and control electronics for scanning and selectively processing image data. In particular, only information from sensor pixels in an area of interest are subject to a/d conversion and processing, the remaining data being clocked from the sensor pixels but ignored. Again, all image data processing is carried out at the electronics.